One-step synthesis of spherical/nonspherical polymeric microparticles using non-equilibrium microfluidic droplets

A simple but versatile microfluidic process is presented for the production of monodisperse polymeric microparticles using non-equilibrium droplets. Oil-in-water (o/w) droplets were formed within microchannels by means of a water-soluble polar organic solvent containing polymer molecules as a dispersed phase. The droplets of solvent were rapidly dissolved into the continuous phase during flow through the microchannel, whereas water-insoluble polymers were precipitated to form monodisperse polymeric particles. In this way, we successfully synthesized particles with sizes significantly smaller than that of the initial droplets, using polystyrene and poly(methyl methacrylate) as the polymer molecules and typically ethyl acetate as the polar solvent. Particles obtained under several different conditions exhibited unique non-spherical morphologies, which were caused by the translocation and segregation of the precipitated polymer and diminishing solvent-rich droplet. We confirmed that various factors influence the particle morphology, including the polymer concentration, molecular weight of the polymer, type of the polar solvent, and the presence of additives in the dispersed phase.